Pipeline cleaning

ABSTRACT

A pipeline cleaning arrangement that includes a cleaning pig with guide units at each end. A tow cable, via a cone, pulls the pig assembly in a forward direction. The tow cable then pulls the cone in a rearward direction. The pig is configured with two cleaning portions that separate in the forward direction to avoid debris collection and abut in the rearwards direction to collect pipeline debris and carry this to the entry point for removal via a suction tube.

The present invention relates to pipeline cleaning and more particularlyto pipeline typically carrying fluid at the time of cleaning, so called‘live’ operation.

In gas mains, for example, debris typically in the form of light dustthrough to heavy bonded scale can build up in the pipeline and it isnecessary to remove this. If excessive this needs to be removed prior toany internal inspection and repair. The effective diameter of the pipewill also become reduced due to such build up. In addition filterblockage in gas governor stations can occur as can valve diaphragmdamage. In the past it has been necessary to shut down the section ofthe pipeline to allow access to the pipeline in a decommissioned state.To do so means interrupting the supply of gas to consumers andassociated problems.

In U.S. Pat. No. 4,827,553 a cleaning device is disclosed with a hingedportion for effecting cleaning.

The present invention is concerned with arrangements which allow thecleaning of the pipeline whilst still allowing the option of supplyinggas or other fluid through the pipeline, even when the gas may be fuelgas or the like.

According to the invention there is provided a cleaning pipe forcleaning debris from a fluid pipeline comprising:

slider means, and first and second cleaning portions,

at least one of said portions cooperating with the slider means topermit movement of the portions towards each other or apart, so as toallow passage of the pigs from a first location to a second locationalong the pipeline without collecting any substantial amount of debriswhen the portions are apart, and to cause cleaning of the pipeline bytransporting debris during passage of the pig from the second to thefirst location when the portions are together, the pig including meansto cause the portions to move towards each other or apart in dependenceon the direction of travel of the pig through the pipeline.

Further according to the invention there is provided a method ofcleaning a pipeline the method comprising:

providing first and second cleaning portions of a pig in slidablerelationship,

moving the pig from a first location to a second location along thepipeline without collecting any substantial amount of debris whilst thecleaning portions are spaced apart, and moving the pig from the secondlocation to the first location along the pipeline so as to cause thecleaning portions to move towards each other so as to allow the pig totransport debris from the second location to the first location, theportions being configured so that they move towards each other or apartin dependence on the direction of travel of the pig through thepipeline.

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 shows the cleaning pig and associated components located in apipeline;

FIG. 2 shows an embodiment of the guide unit structure employed in FIG.1;

FIG. 3 shows the cleaning pig of FIG. 1 in more detail;

FIG. 4 shows the cleaning pig with the two segments shown in theseparated position equivalent to it being towed in the forwarddirection; and

FIG. 5 shows the cleaning pig with the two segments in the abuttingposition equivalent to it being towed in the rearward direction.

The arrangement of FIG. 1 shows a portion of pipeline 10 with acollector or cleaning pig arrangement 12. The arrangement includes atowing cable 13 with tow cone 14 connected to a first guide unit 15.

The guide unit is connected by coupling 16 to a dredging or cleaning pig18. The rear of the pig 18 is itself connected to a second guide unit 20via coupling 19.

The second guide unit 20 is connected to a cone 21 and towing cable 22.

In practice the arrangement is towed in a forward direction by cable 13to a desired position and thereafter towed in a rearward direction bycable 22 to effect cleaning or dredging of the pipeline as described inmore detail below.

Access to the pipeline is via entry point 30 which includes a seal toprevent gas escape around the cable and an entry point at the other endof the pipe section will be provided (not shown) to accommodate thecable 13 in sealed manner.

As an initial step in the cleaning process, prior to insertion of thepig 18, the cable 13 will have been connected following the passage of aparachute type device which is carried down the pipeline by the flow ofgas to the front exit point.

A camera may follow this passage prior to insertion of the pig 18 toensure debris build up is not too great to operate the system. Thecamera will also help establish the length of pipeline that can betraversed before the cleaning operation commences.

Debris dredged by the pig can be removed from the entry point 30 bymeans of a vacuum system terminating in suction tube 32. An arrangementincluding the winch for the cable and camera and control unit togetherwith more details of the sealing arrangements and vacuum device is thesubject of our copending UK patent application 9705182.5.

The construction of the guide units 15 and 20 of FIG. 1 is now shown inmore detail in FIG. 2.

Each guide unit comprises a central bar portion 35 supporting first andsecond guide portions 36 and 37.

The first guide portion includes three legs 39 a-c spaced at 180 degreesand ending in curved shoe portions 40 a-c.

The shoe portions each terminate in a curved plastic (i.e. Delrin) face41 a-c, respectively.

The second guide portion 37 includes three legs 43 a-c spaced at 180degrees and ending in curved shoe portions 44 a-c.

The shoe portions each terminate in a curved plastic face 45 a-c,respectively.

At one end of the bar 35 a simple tow eye 47 is provided to allowconnection to be made to the towing mechanism.

At the other end of the bar 35 is a bearing and tow eye assembly 49 toallow rotation of the tow eye.

It is to be noted that the first guide portion 36 has an overalldiameter that is smaller than that of the second guide portion diameter.This is to facilitate passage through the pipeline as it is pulled bythe towing cable.

In practice the guide units are arranged in the pipeline to each havethe larger diameter portion nearer to the pig 18 to maximize the guidingaction whether the pig is being pulled in a forward or rearwarddirection. The bearing and tow eye assembly 49 on each guide unit willconnect to the pig 18 (as shown in FIG. 1). The gas within the pipelinecan pass through the gaps in the guide units without restriction.

The pig 18 of FIG. 1 is shown in more detail in FIGS. 3 to 5.

The pig 18 is constructed with a bar 52 carrying a first fixed segment53 (see FIG. 3). A second segment 54 is slidably mounted on the bar 52and its travel is limited by contact with either the first segment 53 orshackle 55 affixed to the bar (see also FIG. 4).

The first segment 53 includes three leg portions 56 a-c spaced apart by120 degrees and affixed to the bar 52 (e.g. welded at point 59). The legportions terminate in shoe portions 57 a-c. The shoes carry respectivelyplastic (i.e. polyurethane) blades 58 a-c. The blades are of tripleconstruction but have gaps to accommodate the second sliding segment 54in the return travel (see also FIG. 5).

The blades are positioned 45 degrees offset from each other to cover theentire pipe wall when mated with the second segment.

The second segment 54 has blades 60 a-c are mounted on shoes 61 a-c atthe ends of leg portions 62 a-c spaced at 120 degrees and of tripleconstruction. The leg portions 62 a-c terminate at ring 63 which isfixed to slotted slider 64 to allow the sliding action to be easilyeffected.

In use, the pig within the pipeline 10 (see FIG. 1) will be pulled viaguide unit 15 by the tow cable 13 in a forward direction. As it does sothe two segments will move apart as a result of friction between theblades 60 a-c and the pipe wall causing the segment 54 to slide to itsrearward position.

This separation allows the pig to move over debris without collection,due to the gaps between the blades in both segments. Some of this debrismay have been loosened by the blades on the pigs as it travels.

Once a suitable point in the pipeline has been reached the operation isreversed and the towing cable 22 takes over.

Friction between the blades 60 a-c and the pipe walls will cause thesecond segment to slide until it mates with the first segment (as shownin FIG. 5) thus providing an uninterrupted blade surface to the pipewall and in this mode it scrapes the internal wall releasing depositsand loose debris such as dust using a dredging action. The combinationof blade portions thus form a disk-like profile. Due to the gaps betweenthe legs of the pig, gas can still flow without interruption allowing‘live’ operation, due to this central bypass.

The construction assists in scraping and collecting debris without unduedust swirling which would then be deposited elsewhere. At the point 30the debris can be removed by vacuum techniques via tube 32. The debristogether with any gas extracted will be filtered and the gas remnant canthen be returned to the pipeline.

The polyurethane blades are rigid (typically 25 mm thick), but on apipeline of 8 inches typically carrying gas at 2 bar, the stresses ontowing will cause the blades to distort which assist in the contact withthe pipe wall and hence the scraping action.

The plastic structure of the blades, bend under force so protecting anyservice connections, which may otherwise be damaged by steel or similarblades. The boat shaped blades dig or plough through the material.

The central aperture portion in the scraping and dredging mode stillallows a bypass of about about 3 inches for the gas in the pipeline soensuring continuity of supply.

The cleaning can be effected at a relatively rapid rate of 2meters/second. Other pipe diameters can be accommodated by selectingappropriate dimensions for the pig assembly.

The presence of the guide units assist in maintaining the correctcentral position of the cleaning pig in either direction of travelthrough the pipeline as well as providing guidance at bends in thepipeline (typically 1D blends).

The arrangement allowing travel forward without collection andthereafter to travel rearwards collecting the debris, allows a combinedsingle entry and exit point to be utilised.

I claim:
 1. A cleaning pig for cleaning debris from a fluid pipelinecomprising: slider means, and first and second cleaning portions, atleast one of said portions cooperating with the slider means to permitmovement of the portions towards each other or apart, so as to allowpassage of the pig from a first location to a second location along thepipeline without collecting any substantial amount of debris when theportions are apart, and to cause cleaning of the pipeline bytransporting debris during passage of the pig from the second to thefirst location when the portions are together, the pig including meansto cause the portions to move towards each other or apart in dependenceon the direction of travel of the pig through the pipeline.
 2. A pig asclaimed in claim 1 including means for providing an aperture for fluidflow irrespective to the direction of passage of the pig in thepipeline.
 3. A pig as claimed in claim 2 wherein the means causing theportions to move apart to effect separation include means for contactingthe pipeline wall to allow the second portion to move away from thefirst portion via the slider means due to frictional forces exerted bythe means contacting the wall during travel of the pig from the first tothe second location.
 4. A pig as claimed in claim 3 wherein the meanscausing the portions to move towards each other to effect abutmentinclude means for contacting the pipeline wall or debris to allow thesecond portion to move towards the first portion via the slider meansdue to friction during travel of the pig from the second to the firstlocation so as to collect and transport debris therein.
 5. A pig asclaimed in claim 3 wherein the means for contacting the pipeline wallincludes at least one scraper configured to remove debris from thepipeline wall in at least one direction of travel.
 6. A pig as claimedin claim 5 wherein the at least one scraper comprises a plurality ofplastic blade segments.
 7. A pig as claimed in claim 5 wherein thescraper arrangement on the first portion is configured to locate withinapertures between a scraper arrangement on the second portion.
 8. A pigas claimed in claim 5 wherein a plurality of scrapers are provided eachin the form of resilient elements in combination of generally diskshape.
 9. A pig as claimed in claim 1 including guide means configuredto be located both in front and to the rear of the pig during travelthrough the pipeline, the guide means assisting in maintaining thecorrect position of the pig within the pipeline.
 10. A pig as claimed inclaim 9 wherein the guide means each include a body portion carrying aplurality of legs terminating in shoe portions configured to contact thepipeline wall during travel.
 11. A pig as claimed in claim 10 whereineach guide means includes two separate sections each carrying aplurality of legs terminating in shoe portions, the shoe portionconfigured to be adjacent the pig during travel extending closer to thepipeline wall in use than the other shoe portion.
 12. A pig as claimedin claim 1 including a towing cable for moving the pig in a forwarddirection and a towing cable for moving the pig in a reverse direction.13. A method of cleaning a pipeline the method comprising the steps of:providing first and second cleaning portions of a pig in slidablerelationship, moving the pig from a first location to a second locationalong the pipeline without collecting any substantial amount of debriswhilst the cleaning portions are spaced apart, and moving the pig fromthe second location to the first location along the pipeline so as tocause the cleaning portions to move towards each other so as to allowthe pig to transport debris from the second location to the firstlocation, the portions being configured so that they move towards eachother or apart in dependence on the direction of travel of the pigthrough the pipeline.
 14. A method as claimed in claim 13 including thestep of providing an aperture in the pig to allow fluid flow through thepipeline.
 15. A method as claimed in claim 13 including the step ofabutting the first and second cleaning portions so as to form aplurality of disk shaped segments having a scraping action.
 16. A methodas claimed in claim 13, including the step of providing guide means bothin front and to the rear of the pig to assist in maintaining the pig inthe correct position within the pipeline.
 17. A method as claimed inclaim 13 including the step of towing the pig in a forward or reversedirection to effect movement.